1. Field of the Invention
The present invention relates to the field of power inverters used for electronic lighting ballast and the ability of the ballast to monitor the incoming power line for control signals to adjust the operation of the ballast. In the process of monitoring the power line the microprocessor within the ballast can detect, among other control signals, the amount of phase chop caused by a conventional wall dimmer and adjust the light output accordingly. The method of driving a flat panel or electro luminescent display is also disclosed.
2. Brief Description of the Prior Art
There are many varied public domain circuits involving the generation of high frequency inputs for driving fluorescent lamps, compact fluorescent lamps, high intensity discharge and other forms of gas discharged lighting. With more and more emphasis being placed on energy conservation controllable output or dimming ballasts are becoming more in demand. The problem now is that there is a need for a mechanism to determine the proper level at which to operate the ballast as well as an inexpensive and reliable method of communicating this control information to the ballast. Ballasts that have the capability of adjusting light output, with a corresponding reduction of power input, and the ability of communicating with a lighting system have been, up to now, considerably more complicated and expensive to produce. Thus, there are no ballasts that are capable of performing the necessary tasks while still being low enough in cost to be used in all locations. New and different means of lighting an area are also entering the market. Electro luminescent panels originally developed for computer monitors are being used now as sources of illumination is some cases. These panels also need a ballast but they must operate at low frequency compared to fluorescent lighting ballasts. In most applications they have been found difficult to drive efficiently. It is often desirable to connect a ballast to a system that uses some form of interruption of a portion of the power line cycle. This is referred to as ‘phase chop dimming’. Most electronic devices have some sort of regulation that compensates for this until so much of the line sine wave is eliminated that dimming is not functional.